This invention relates to the production of aromatic diamino compounds by hydrogenating aromatic dinitro compounds in the presence of a modified Raney catalyst.
The catalytic hydrogenation of aromatic dinitro coapounds, such as dinitrotoluene, using suspended Raney catalysts is known (see, e.g. DE-AS No. 1,044,099 and FR-PS No. 1,599,004). Such hydrogenation generally takes place at temperatures below 170.degree. C., preferably at temperatures of from 50.degree. to 150.degree. C. The heat of the hydrogenation reaction is deliberately lost in order to obtain the desired diamines in high yields and at high purities.
Processes which allow a reaction to be carried out at high temperatures, such as that described in DE-OS No. 3,315,191, require improved catalysts having increased selectivity and elevated temperature resistance. Important secondary reactions in this context are hydrogenation and deamination of the aromatic moieties, as well as the formation of high molecular weight compounds.